JP4570622B2 - Lubricant for recording medium and magnetic disk - Google Patents

Description

  The present invention relates to a lubricant for a recording medium such as a magnetic disk and a magnetic tape, and a magnetic disk having a lubricant layer formed using the lubricant.

As a lubricant for a magnetic disk, a perfluoropolyether compound is generally used. Among them, a Fomblin-based compound manufactured by Solvay, which has a low surface energy and a low frictional force, is mainly used. Fomblin compounds are perfluoropolyether compounds whose basic skeleton of the main chain is (CF ₂ CF ₂ O) _m (CF ₂ O) _n .

However, it is known that fomblin compounds react with alumina (Al ₂ O ₃ ) contained in the head member to cause the main chain to break (Macromolecules, 1992, Vol. 25, p. 6791). -6799). As this cutting proceeds, the perfluoropolyether has a low molecular weight and eventually has the disadvantage of volatilizing from the magnetic disk.

  On the other hand, the magnetic disk drive drive system includes a contact start / stop (CSS) system in which the head and the disk come into contact with each other when the apparatus is started / stopped, and ramp / load / There is an unload (L / UL) system, and the required characteristics for the lubricant differ depending on the system.

  In recent years, there has been a demand for higher recording density and higher speed processing of disk devices. Correspondingly, it is necessary to reduce the distance (flying height) between the head and the disk and to increase the rotation speed of the disk. Basically, even in the L / UL system where the head and the disk do not contact each other, the contact frequency between the head and the disk increases as the flying height decreases and the speed increases, and the lubricant moves from the disk surface to the head. Or scatter outside. As a result, the disc may be damaged, so that the lubricant having a strong adhesion to the disc surface is desirable. As such a lubricant, there is a fomblin perfluoropolyether compound (for example, “Z-Tetraol” manufactured by Solvay) having a plurality of polar groups in the molecule. This lubricant is decomposed by alumina. The problem of getting up has not been solved.

  On the other hand, a compound in which the end of the perfluoropolyether skeleton is modified with a phosphazene functional group is known as a compound that suppresses the decomposition reaction by alumina despite having a perfluoropolyether chain in the molecule. (US Pat. No. 6,608,009, US Pat. No. 6,605,335). These compounds are inhibited from being decomposed by alumina due to the effect of the modified phosphazene functional group. In addition, it has high compatibility with other perfluoropolyether compounds and has excellent CSS resistance. However, the adhesive force with the disk surface is low, which is not preferable as a lubricant for the L / UL system.

  In order to increase the speed of recording / reproducing information, the rotational speed of the magnetic disk is expected to be 15,000 rpm or more in the near future. As the rotational speed of the magnetic disk increases, the amount of lubricant scattered tends to increase. In addition, if the sliding is performed for a long time while rotating at a high speed, the lubricating layer becomes thin due to the decomposition, and eventually the magnetic disk is destroyed. In order to ensure the reliability of the magnetic disk drive, a lubricant that has strong adhesion to the magnetic disk and is difficult to disassemble is required.

  An object of the present invention is to provide a lubricant for a recording medium that has a strong adhesion to the recording medium and is difficult to decompose.

  The present invention provides a lubricant for a recording medium and a magnetic disk as described below.

1. Formula (1);
R ¹ —CH ₂ CF ₂ O— (CF ₂ CF ₂ O) _m — (CF ₂ O) _n —CF ₂ CH ₂ —R ² (1)
[Wherein R ¹ is

(R represents a C _1-4 haloalkyl group), R ² represents —OCH ₂ CH (OH) CH ₂ OH, and m and n each represent 1 to 30. A perfluoropolyether compound represented by the formula (2);
R ¹ —CH ₂ CF ₂ O— (CF ₂ CF ₂ O) _m — (CF ₂ O) _n —CF ₂ CH ₂ —R ³ (2)
[Wherein, R ¹ , m and n are the same as defined above, and R ³ represents —OCH ₂ CH (OH) CH ₂ OCH ₂ CH (OH) CH ₂ OH]. ] The lubricant for recording media containing the perfluoropolyether compound represented by this.

  2. A magnetic disk in which a recording layer and a protective layer are formed in this order on a support, and a lubricating layer made of the lubricant according to Item 1 is formed on the surface of the protective layer.

  Hereinafter, the present invention will be described in detail.

  The perfluoropolyether compound contained in the recording medium lubricant of the present invention comprises a plurality of hydroxyl groups having a cyclotriphosphazene functional group at one end of a perfluoropolyether chain and a glycol skeleton at the other end. Have

  The lubricant for recording media of the present invention is produced, for example, as follows.

The main chain is —CH ₂ CF ₂ O— (CF ₂ CF ₂ O) _m — (CF ₂ O) _n —CF ₂ CH ₂ —, wherein m and n each represent 1 to 30. ], A perfluoropolyether compound having a cyclotriphosphazene functional group at one end and one hydroxyl group at the other end, potassium t-butoxide, and t-butanol are mixed, For 30 minutes. After potassium-t-butoxide is dissolved, 0.5-2.0 equivalents of 2,3-epoxy-1-propanol are slowly added dropwise over 2 hours with stirring at 70 ° C. After completion of dropping, the mixture is further stirred at 70 ° C. for 2 hours. After completion of the reaction, extraction is performed with a perfluorocarbon solvent, and the solvent is distilled off by distillation to obtain a viscous liquid. The resulting viscous liquid is a perfluoropolyether compound represented by the above formula (1), a perfluoropolyether compound represented by the above formula (2), and a formula (3);
R ¹ —CH ₂ CF ₂ O— (CF ₂ CF ₂ O) _m — (CF ₂ O) _n —CF ₂ CH ₂ —OH (3)
[Wherein R ¹ is

(R represents a C _1-4 haloalkyl group), and m and n each represent 1 to 30. ] The perfluoro polyether compound represented by this is contained.

  This three-component mixture can be used as it is as a lubricant for recording media of the present invention, but it can also be used after being purified by a purification method such as column chromatography or supercritical carbonic acid extraction.

  As the recording medium lubricant, the total content of the perfluoropolyether compound represented by the above formula (1) and the perfluoropolyether compound represented by the above formula (2) is 50% by weight or more, and The content of the perfluoropolyether compound represented by the formula (1) is preferably 30% by weight or more, and is represented by the perfluoropolyether compound represented by the above formula (1) and the above formula (2). More preferably, the total content of the perfluoropolyether compound is 70% by weight or more and the content of the perfluoropolyether compound represented by the above formula (1) is 40% by weight or more.

The main chain of the production raw material is —CH ₂ CF ₂ O— (CF ₂ CF ₂ O) _m — (CF ₂ O) _n —CF ₂ CH ₂ —, wherein m and n each represent 1 to 30 . ] As a perfluoropolyether compound having a cyclotriphosphazene functional group at one end and one hydroxyl group at the other end, for example, "Molescophospharol manufactured by Matsumura Oil Research Co., Ltd." A20H ". The chemical structure of this _{compound, (CF 3 C 6 H 4} O) 5 -P 3 N 3 -CH 2 CF 2 O- (CF 2 CF 2 O) m - (CF 2 O) n -CF 2 CH 2 OH [ In the formula, —P ₃ N ₃ — represents a cyclotriphosphazene ring, and m and n each represents 1 to 30. The number average molecular weight is about 1300-8000.

  The use of the recording medium lubricant of the present invention includes use as a lubricant for improving the sliding characteristics of the magnetic disk in the magnetic disk apparatus. The purpose of this is to reduce the coefficient of friction between the magnetic disk and the head, so that it can be used as a lubricant in other recording devices that involve sliding between the recording medium such as magnetic tape and the head in addition to the magnetic disk. Also mentioned. In addition, the present invention is not limited to a recording apparatus, and may be used as a lubricant for equipment having a sliding part. In addition, since the lubricant of the present invention also exhibits an effect of suppressing the decomposition of the fomblin perfluoropolyether compound, it can be used in combination with a fomblin lubricant. Further, it can be used in combination with a lubricant other than Fomblin (for example, “Demnam SA” manufactured by Daikin Industries, Ltd., “Crytox” manufactured by Solvay).

  The magnetic disk of the present invention is formed by forming a recording layer and a protective layer in this order on a support, and forming a lubricating layer made of the recording medium lubricant on the surface of the protective layer.

  FIG. 1 shows an outline of the configuration (cross section) of an example of the magnetic disk of the present invention.

  In FIG. 1, the magnetic disk of the present invention has a recording layer 2 on a support 1, a protective layer 3 thereon, and a lubricating layer 4 made of the above-described recording medium lubricant. It has as the outermost layer.

Examples of the material for the support 1 include aluminum alloy, glass, and polycarbonate. Examples of the material of the recording layer 2 include alloys obtained by adding chromium, platinum, tantalum, and the like to elements capable of forming a ferromagnetic material such as iron, cobalt, and nickel, or oxides thereof. These are formed by plating, sputtering, or the like. Examples of the material for the protective layer 3 include diamond-like carbon, Si ₃ N ₄ , SiC, and SiO ₂ . These are formed by sputtering, CVD, or the like.

  The lubricating layer 4 is usually formed by a dipping method using the recording medium lubricant of the present invention dissolved in a solvent and using this solution. As the solvent, a solvent capable of dissolving the recording medium lubricant of the present invention is used. Specifically, fluorocarbon solvents (for example, “PF-5060”, “PF-5080”, “HFE-7100”, “HFE-7200” manufactured by Sumitomo 3M, “Bertrel XF” manufactured by DuPont) Etc.

  Since the recording medium lubricant of the present invention has a strong adhesion to the recording medium, scattering can be reduced and it is difficult to decompose. A magnetic disk having a lubricating layer formed using the lubricant can withstand continuous sliding under high-speed rotation, and a magnetic disk drive equipped with the magnetic disk can record / reproduce at high speed. become.

FIG. 1 is a schematic sectional view showing an example of the magnetic disk of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Support body 2 Recording layer 3 Protective layer 4 Lubrication layer

  Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1
Under an argon atmosphere, 22.0 g (7.11 mmol) of “Molescophosphalol A20H-2000” manufactured by Matsumura Oil Research Co., Ltd., 0.1 g (0.71 mmol) of potassium-t-butoxide and t-butanol 13. 0 ml was mixed and stirred at 70 ° C. for 30 minutes. After the dissolution of potassium-t-butoxide, 0.6 g (7.11 mmol) of 2,3-epoxy-1-propanol was added dropwise over 2 hours with stirring at 70 ° C. After completion of dropping, the mixture was further stirred at 70 ° C. for 2 hours. After completion of the reaction, the reaction mixture was extracted by adding “Bertrel XF” manufactured by DuPont, and washed with an aqueous solution obtained by mixing 1N hydrochloric acid and methanol. “Bertrel XF” was distilled off by distillation to obtain 14.0 g of a viscous liquid.

The obtained viscous liquid was subjected to ¹⁹ F-NMR analysis and ¹ H-NMR analysis, and the number average molecular weight and composition (% by weight) were calculated. The number average molecular weight was 2929. The composition is shown in Table 1. In Table 1, the compound of the formula (1) is a perfluoropolyether compound represented by the above formula (1) in which R is a trifluoromethyl group. The compound of the formula (2) is a perfluoropolyether compound represented by the above formula (2) in which R is a trifluoromethyl group. The compound of the formula (3) is a perfluoropolyether compound represented by the above formula (3) in which R is a trifluoromethyl group.

Hereafter, a < ¹⁹ > F-NMR analysis result is shown.
¹⁹ F-NMR (solvent: none. Reference substance: OCF ₂ CF ₂ CF ₂ CF ₂ O in the product was set to −125.8 ppm):
δ = −78.6 ppm, −80.6 ppm
_{[2F, Rf- [CF 2 CH 2} -O-P 3 N 3 - (OC 6 H 4 CF 3) 5] ],
δ = -77.8 ppm, -79.9 ppm
_{[2F, Rf- [CF 2 CH 2} -O-CH 2 CH (OH) CH 2 OH] ].

Trifluoroacetylation was performed as a pretreatment for ¹ H-NMR analysis. As a procedure, 2.0 g of 10-fold amount of trifluoroacetic anhydride was added to 0.2 g of viscous liquid, and the mixture was stirred at room temperature for 12 hours. After completion of the stirring, excess trifluoroacetic anhydride was distilled off to obtain a trifluoroacetylated product.

The results of ¹ H-NMR analysis are shown below.
¹ H-NMR [trifluoroacetylated compound] (solvent: perfluorohexane, reference substance: heavy water D ₂ O):
δ = 3.70-4.05 ppm
_{[4H, Rf- [CF 2 CH 2} -O- CH 2 CH (OAc) CH 2 OAc] ],
δ = 3.70-4.05 ppm
_{[2H, Rf- [CF 2 CH 2} -O-P 3 N 3 - (OC 6 H 4 CF 3) 5] ],
δ = 4.45-4.70 ppm
_{[2H, Rf- [CF 2 CH 2} -O-CH 2 CH (OAc) CH 2 OAc] ],
δ = 5.25-5.35 ppm
_{[1H, Rf- [CF 2 CH 2} -O-CH 2 CH (OAc) CH 2 OCH 2 CH (OAc) CH 2 OAc] ],
δ = 5.37-5.57 ppm
_{[1H, Rf- [CF 2 CH 2} -O-CH 2 CH (OAc) CH 2 OAc] ].

Example 2
Under an argon atmosphere, 67.0 g (0.022 mol) of “Molecophospharol A20H-2000” manufactured by Matsumura Oil Research Co., Ltd., 0.3 g (0.002 mol) of potassium-t-butoxide and 30. 0 ml was mixed and stirred at 70 ° C. for 30 minutes. After the dissolution of potassium t-butoxide, 2.0 g (0.022 mol) of 2,3-epoxy-1-propanol was added dropwise over 2 hours with stirring at 70 ° C. After completion of dropping, the mixture was further stirred at 70 ° C. for 2 hours. After completion of the reaction, the reaction mixture was extracted by adding “Bertrel XF” manufactured by DuPont, and washed with an aqueous solution obtained by mixing 1N hydrochloric acid and methanol. After distilling off “Bertrel XF” by distillation, purification was performed by supercritical carbonic acid extraction to obtain 22.3 g of viscous liquid.

The obtained viscous liquid was subjected to ¹⁹ F-NMR analysis and ¹ H-NMR analysis, and the number average molecular weight and composition (% by weight) were calculated. The number average molecular weight was 3130. The composition is shown in Table 2. In Table 2, the compound of formula (1), the compound of formula (2) and the compound of formula (3) are the same as in Table 1.

  The chemical shift of NMR analysis was the same as in Example 1.

  About the viscous liquid (lubricant) obtained in Examples 1 and 2, the bond rate was measured and the decomposition resistance test for alumina was performed.

[Measurement of bond rate]
The viscous liquid (lubricant) obtained in Examples 1 and 2 was dissolved in “Bertrel XF” manufactured by DuPont to prepare each lubricant solution (0.1 wt%). A glass media magnetic disk having a diameter of 2.5 inches was immersed in a lubricant solution for 1 minute, pulled up at a speed of 2 mm / s and coated with a lubricant, and then the magnetic disk was placed in a thermostat at 100 ° C. for 20 minutes and heated. . The film thickness of the lubricant on the disk was measured with an ellipsometer (this film thickness is defined as eÅ). Next, this disk was immersed in “Bertrel XF” for 10 minutes and pulled up at a speed of 10 mm / s to wash away any lubricant that had not adhered. The film thickness of the lubricant remaining on the disk was measured with an ellipsometer (this film thickness is defined as fÅ). The strength of adhesion to the disk was evaluated using the bond rate represented by the following formula. The results are shown in Table 3.

Bond rate (%) = 100 × f / e
Of the compound of formula (1), the compound of formula (2) and the compound of formula (3) contained in the viscous liquid (lubricant) obtained in Examples 1 and 2, formula (3) Are removed by the above washing. Therefore, the compound of the formula (1) and the compound of the formula (2) having strong adhesive force remain on the disk.

  For comparison, as perfluoropolyter compounds, the same applies to “Molecophospharol A20H-2000” manufactured by Matsumura Oil Research Co., Ltd., “Zdol-4000” and “Z-Tetraol-2000S” manufactured by Solvay. The bond ratio was measured by the method described above. The results are shown in Table 3.

  From Table 3, it was confirmed that the viscous liquid (lubricant) obtained in Examples 1 and 2 can form a lubricating layer that adheres strongly to the magnetic disk. As a result, an effect of reducing the scattering of the lubricant can be expected.

[Decomposition resistance test for alumina]
The viscous liquid (lubricant) obtained in Examples 1 and 2, and "Moleco Phosphorol A20H-2000" manufactured by Matsumura Oil Research Co., Ltd., "Zdol-4000" and "Z-" manufactured by Solvay To each of “Tetolaol-2000S”, alumina powder (average particle size of 100 μm) was added to 20 wt%, and mixed for 15 minutes or more using a shaker. About the sample mixed uniformly, the decomposition resistance test by heating was implemented using the thermal-analysis apparatus (TG / DTA). In the test, a sample mixed with alumina and a sample not mixed were weighed in an aluminum container and heated at a temperature of 250 ° C. in a nitrogen atmosphere, and the weight reduction rate of the sample was measured. The results are shown in Table 4.

  From Table 4, it was confirmed that the viscous liquid (lubricant) obtained in Examples 1 and 2 was excellent in decomposition resistance against alumina.

Example 3
The viscous liquid (lubricant) obtained in Example 1 was dissolved in “Bertrel XF” manufactured by DuPont to prepare a lubricant solution (0.1 wt%). A glass media magnetic disk having a diameter of 2.5 inches composed of a support, a recording layer, and a protective layer is immersed in a lubricant solution for 1 minute, pulled up at a speed of 2 mm / s, applied with a lubricant, and then placed in a constant temperature bath at 100 ° C. The magnetic disk was put in for 20 minutes and heated. Next, this disk was immersed in “Bertrel XF” for 10 minutes, and was pulled up at a speed of 10 mm / s to be cleaned. The film thickness of the lubricant remaining on the disk was measured with an ellipsometer. The film thickness of the lubricant was 4.9 mm.

Claims (2)

Formula (1);
R ¹ —CH ₂ CF ₂ O— (CF ₂ CF ₂ O) _m — (CF ₂ O) _n —CF ₂ CH ₂ —R ² (1)
[Wherein R ¹ is

(R represents a C _1-4 haloalkyl group), R ² represents —OCH ₂ CH (OH) CH ₂ OH, and m and n each represent 1 to 30. A perfluoropolyether compound represented by the formula (2);
R ¹ —CH ₂ CF ₂ O— (CF ₂ CF ₂ O) _m — (CF ₂ O) _n —CF ₂ CH ₂ —R ³ (2)
[Wherein, R ¹ , m and n are the same as defined above, and R ³ represents —OCH ₂ CH (OH) CH ₂ OCH ₂ CH (OH) CH ₂ OH]. ] The lubricant for recording media containing the perfluoropolyether compound represented by this.   A magnetic disk in which a recording layer and a protective layer are formed in this order on a support, and a lubricating layer made of the lubricant according to claim 1 is formed on the surface of the protective layer.

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